Vitamin D3 is vitamin D3, and the best time of day to take it is generally between 8:00 a.m. and 9:00 a.m., and it is appropriate to take it before meals and on an empty stomach. Vitamin D3 can improve the body’s absorption of calcium and phosphorus, promote growth and bone calcification, and is often used to prevent and treat vitamin D deficiency, such as rickets. Since vitamin D3 is generally absorbed faster between 8am-9am, it is best to supplement before breakfast. Secondly, vitamin D3 is also known as the sunshine vitamin. The morning sun is more abundant and maintaining a certain amount of sunlight exposure can enhance its effect and help promote calcium absorption. Calcium deficiency in newborns often manifests as agitation, night terrors, sweating, etc., and in severe cases, growth retardation. When taking vitamin D3 it is recommended to start half a month after birth to effectively prevent calcium deficiency. While taking vitamin D3, patients are advised to do more outdoor activities and keep sufficient sunlight exposure; at the same time, eat a light diet with foods rich in calcium, protein and vitamins; take calcium supplements when necessary and maintain a happy mood.